Melania's last public appearance was on May 10, when she joined President Trump to welcome home the three Americans released from North Korea.
"I see the media is working overtime speculating where I am & what I'm doing", the account tweeted.
She was most recently seen in public on 10 May at Joint Base Andrews in Maryland, when she accompanied her husband as he greeted returning United States citizens who had been released from North Korea.
First ladies are under no obligation to make their medical histories public, and the White House has said nothing more about Mrs. Trump's condition.
Still, it looks like a lot of Twitter users are just refusing to believe she is alright. "She was hospitalized for nearly a week and is now home and recovering".
Philippines says it protests China ‘harassment’ of navy boat
The disinvite was described as an "initial response to China's continued militarization of the South China Sea". Mattis was heading to Hawaii to attend a change-of-command ceremony for the USA military's Pacific Command.
Twenty-four hours before he takes the oath of office as the 45th U.S. president, Trump arrived in Washington on Thursday, determined to transform American politics over the next four years. "She is doing great".
In a rare Twitter appearance to do something other than appropriately mark an occasion (her most recent tweets have been about the Santa Fe massacre, awarding the Medal of Honor, and Memorial Day), Melania put the media's alleged concerns to rest about her whereabouts. "She seems to be recovering well", he said, though he offered no further details.
They say she feels people are being nosey, rather than genuinely concerned about her, and that she has no desire to reveal any information as a result.
Nonetheless, she outshone the President, and the French President and first lady, in late-April, wearing a scene-stealing white hat to an official South Lawn arrival ceremony, garnering comparisons to Beyoncé. But her office has dismissed these theories, saying she's back at work and has been involved in internal meetings this week.
She also tweets when she feels like it, without waiting - or even asking - for West Wing approval or coordination. I wouldn't characterise it as a long absence.
In April, she alone represented the administration at the Houston funeral of former first lady Barbara Bush.